fsm_book

This method for estimating total FS production will result in an overestimation of the potential
volumes to be delivered to a FSTP. Although the ultimate goal is for all FS to be delivered to a treatment
plant, it is not realistic to assume that all of the FS produced will initially be collected and transported
for discharge at a FSTP.
Technology
2.2.2 Sludge collection method
The quantity of FS that is currently being collected from onsite systems in an area will vary depending
on the FSM infrastructure, based on factors such as acceptance and promotion of FSM, demand for
emptying and collection services, and availability of legal discharge or treatment sites. The volume that
is currently being collected can be estimated based on interviews, site visits, and a review of internal
records of FS collection and transport companies. Estimates can be based on the number of collections
made each day, the volume of FS per collection, the average emptying frequency at the household level,
and the estimated proportion of the population that employ the services of collection and transport
companies (Koanda, 2006). The activity of informal or illegal collection should also be taken into
account, as the volumes collected can be quite significant.
Estimating generation of FS based on this method is complicated by many factors such as the presence
of a legal discharge location or treatment plant (see Figure 2.1), if the discharge fees are affordable, and
whether there are enforcement measures to control illegal dumping. If all of these factors are in place,
then it is possible that the majority of the FS collected will be transported and delivered to a treatment
site. If a legal discharge location exists, a flow meter can be installed in order to provide an indication of
the volume of FS that is being discharged. However, there is currently a lack of legal discharge locations,
and, collection and transport companies are hesitant to cooperate in an official study that effectively
documents their illegal activities. It is difficult to quantify the volume of FS being dumped illegally
directly into the environment, either by collection and transport companies, or by households that
hire manual laborers to remove FS. In addition, if volumes are being estimated for a treatment plant in
an area where no legitimate discharge option currently exists, once it is built, it is expected to rapidly
increase the market for these services, and hence the volume that will be delivered will also increase.
This could result in an underestimation of the required capacity for the FSTP.
Figure 2.1
Discharge of faecal sludge at Duombasie landfill and faecal sludge treatment site in Kumasi, Ghana
(photo: Linda Strande).
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